CATV networks use an infrastructure of interconnected coaxial cables, signal splitters and combiners, repeating amplifiers, filters, trunk lines, cable taps, drop lines and other signal-conducting devices to supply and distribute high frequency “downstream” signals from a main signal distribution facility, known as a “headend,” to the premises (homes and offices) of subscribers to the CATV services. The downstream signals operate subscriber equipment, such as television sets, telephone sets and computers. In addition, most CATV networks also transmit “upstream” signals from the subscriber equipment back to the headend of the CATV network. For example, the subscriber uses a set top box to select programs for display on the television set. As another example, two-way communication is essential when using a personal computer connected through the CATV infrastructure to the public Internet. As a further example, voice over Internet protocol (VOIP) telephone sets use the CATV infrastructure and the public Internet as the communication medium for transmitting two-way telephone conversations.
To permit simultaneous communication of upstream and downstream CATV signals and the interoperability of the subscriber equipment and the equipment associated with the CATV network infrastructure outside of subscriber premises, the downstream and upstream signals are confined to two different frequency bands. The downstream frequency band is within the range of 54-1002 megahertz (MHz) and the upstream frequency band is within the range of 5-42 MHz, in most CATV networks.
The downstream signals are delivered from the CATV network infrastructure to the subscriber premises at an entry device, which is also commonly referred to as an entry adapter, terminal adapter or a drop amplifier. The entry device is usually a multi-port device which provides a multiplicity of ports or connectors for connecting coaxial cables. A separate coaxial cable is connected to each of the ports and extends within the subscriber premises to the location of the subscriber equipment. Typically, most homes have coaxial cables extending to cable outlets in almost every room, because different types of subscriber equipment may be used in different rooms. For example, television sets and computers may be present in many different rooms. One or more telephone sets are also commonplace in a home. The multiple ports on the entry device accommodate connections to the subscriber equipment so that the downstream signals are received at each cable outlet and upstream signals are conducted back through the premises coaxial cables to the entry device and from there as upstream signals on the CATV network.
In addition to television sets, computers and telephones, a relatively large number of other entertainment and multimedia devices are available for use in homes. For example, a digital video recorder (DVR) is used to record broadcast programming, still photography and moving pictures in a memory medium so that the content can be replayed on a display or television set at a later time selected by the user. As another example, computer games are also played at displays or on television sets. Such computer games may be those obtained over the Internet from the CATV network or from media played on play-back devices connected to displays or television sets. As a further example, receivers which receive satellite-broadcast signals may be distributed for viewing or listening throughout the home. These types of devices, including the more-conventional television sets, telephone sets and devices connected to the Internet by the CATV network, are generically referred to as multimedia devices.
The desire to use multimedia devices at multiple different locations within the home or subscriber premises has led to the creation of the Multimedia over Coax Alliance (MoCA). MoCA has developed specifications for products to create an in-home entertainment network for interconnecting presently-known and future multimedia devices. The MoCA in-home network uses the subscriber premise or in-home coaxial cable infrastructure originally established for distribution of CATV signals within the subscriber premises, principally because that cable infrastructure already exists in most homes and is capable of carrying much more information than is carried in the CATV frequency bands. A MoCA network is established by connecting MoCA interface devices at the cable outlets in the rooms of the subscriber premises. The MoCA interface devices implement a MoCA communication protocol which encapsulates the signals normally used by the multimedia devices within MoCA signals and then communicate these MoCA signals between selected ones of the other MoCA interfaces devices connected at other cable outlets. The receiving MoCA interface device removes the encapsulated multimedia device signals, and delivers those to the connected display, computer or other multimedia device from which the content is presented.
Each MoCA interface device is capable of communicating with every other MoCA interface device in the MoCA network to deliver the multimedia content throughout the home or subscriber premises. The entertainment or multimedia content that is available from one multimedia device can be displayed, played or otherwise used at a different location within the home, without having to physically relocate the multimedia device from one location to another within the home. The in-home network communication of multimedia content is considered beneficial in more fully utilizing the multimedia devices present in modern homes.
Since the MoCA network may function simultaneously with the normal operation of the CATV services, the MoCA signals communicated between MoCA interface devices utilize a frequency range of 1125-1525 MHz. This so-called D band of MoCA signals is divided into eight different frequency ranges, D1-D8, and these eight different D frequency ranges are used to assure communication between the selected MoCA interface devices. For example, the D-1 band at 1125-1175 MHz may be used to communicate CATV television programming content between a MoCA interface device connected to a set-top box in a main room of the house and another MoCA interface device connected to a television set in bedroom of the house, while a MoCA interface device connected to a computer gaming multimedia device in a basement room of the house simultaneously communicates computer game content over the D-6 band at 1375-1425 MHz to a computer located in a recreation room of the house. The MoCA frequency band also includes other frequency ranges, but the D band is of the major relevance because of its principal use in establishing connections between the MoCA interface devices.
Although using the in-home coaxial cable as the principal communication medium substantially simplifies the implementation of the MoCA network, there are certain disadvantages to doing so. The D band MoCA frequencies have the capability of passing through the CATV entry device and entering the CATV network where they may then pass through a cable drop and enter an adjoining subscriber's premises. The presence of the MoCA signals at an adjoining subscriber's premises compromises the privacy and security of the information originally intended to be confined only within the original subscriber premises. The MoCA signals from the original subscriber premises which enter through the CATV network to adjoining subscriber premises also have the potential to adversely affect the performance of a MoCA network in the adjoining subscriber premises. The conflict of the signals from the original and adjoining subscriber premises may cause the MoCA interface devices to malfunction or not operate properly on a consistent basis.
CATV networks are subject to adverse influences from so-called ingress noise which enters the CATV network from external sources, many of which are located at the subscriber premises. The typical range of ingress noise is in the frequency band of 0-15 MHz, but can also exist in other upstream or downstream frequencies. Ingress noise mitigation devices have been developed to suppress or reduce ingress noise from the subscriber premises before it enters the CATV network. The D bands in the MoCA frequency range are considerably outside the range of the normal ingress noise, and ingress noise suppression devices are ineffectual in inhibiting MoCA signals. MoCA signals, being outside of the CATV signal frequency, may also constitute another source of noise for the CATV network. Separate MoCA frequency rejection filters have been developed for external connection to CATV entry adapters. However, the use of such devices is subject to unauthorized removal, tampering, forgetfulness in original installation, and physical exposure which could lead to premature failure or malfunction.
Problems also arise because the CATV network and the in-home cable infrastructure were originally intended for the distribution of CATV signals to the cable outlets. The typical in-home cable infrastructure uses signal splitters to divide a single downstream signal into multiple downstream signals and to combine multiple upstream signals into a single upstream signal or band. Distribution of the CATV signals to and from the cable outlets occurs in this manner. The CATV cable infrastructure was not intended for communication between cable outlets, but to implement the MoCA communication protocol, the MoCA signals must traverse between the multiple cable outlets by communication through each splitter in a traversal process referred to as “splitter jumping.”
The typical signal splitter has a high degree of signal rejection or isolation between its multiple output ports. When the MoCA signals jump the output ports of a splitter, the degree of signal rejection or isolation greatly diminishes the strength of the signals which effectively jump the output ports. The physical signal communication paths between the cable outlets is also highly variable because of the differences in the in-home cable infrastructure in most homes. The MoCA communication protocol recognizes the possibility of variable strength signals, and provides a facility to boost the strength of MoCA signals under certain circumstances. However, the substantial differences in the in-home cable infrastructure may nevertheless negatively impact the strength of the MoCA signals conducted.
One example of significant negative impact on MoCA signals arises from passive-active CATV entry adapters. Passive-active CATV entry adapters supply both passive CATV signals and amplified or active CATV signals at the subscriber premises for delivery to passive and active types of CATV subscriber equipment, respectively. Passive-active entry adapters include a splitter which essentially divides or branches the downstream signals from the CATV network into passive signals and into active signals. The passive signals are conducted through the entry adapter without amplification, conditioning or modification before they are delivered from a passive port to passive subscriber equipment, typically a voice modem of a “life-line” telephone set. Because life-line telephone services are intended to remain useful in emergency conditions, the functionality of the telephone set can not depend on the proper functionality of an amplifier or other active signal conditioner in the signal path. The active signals are conducted through a forward path amplifier, where the amplifier amplifies the strength of the signals or modifies or conditions some characteristic of the signals before delivery from active ports to active subscriber equipment. Because most subscriber equipment benefits from amplified signals, the majority of ports on a CATV entry adapter are active ports. Usually only one passive port is provided for each entry adapter.
In those situations where a CATV subscriber does not utilize the passive port for passive equipment, active equipment may be connected to the passive port and that active equipment may function properly if the strength of the signal from the passive port is sufficient. In other cases, the passive port simply may not be connected, and only the active ports of the CATV entry adapter are used.
Any attempt to connect the passive port as part of a MoCA network will not be successful, however, because the MoCA signals are severely diminished in signal strength when they pass from the active ports in a reverse direction through the forward path amplifier. The MoCA signals must pass in a reverse direction through the forward path amplifier to reach the splitter of the CATV entry adapter before the MoCA signals can jump the splitter and reach the passive port. Signal conductivity in the reverse direction through a forward path amplifier is simply not possible without severe attenuation. Thus, it is essentially impossible to use a passive port on a CATV entry adapter for connection in a MoCA network, because of inadequate MoCA signal strength. The level of attenuation is greater than can be overcome by adjusting the boost of the MoCA signals in accordance with the MoCA communication protocol.